326 



FATS 



These particles differ in shape and size, ns obtained from different animals ; those of 

 the calf, ox, sheep, are polygonal, and from ^th to ^-th of an inch in diameter ; those 

 of the sow are kidney-shaped, and from ~jth to r^th ; those of man are polygonal, and 

 from ith to ^jth ; those of insects are spherical, and at most ^jjth of an inch. 



Fats all melt at a temperature much under 212 F. When strongly heated with 

 contact of air, they diffuse white pungent fumes, then blacken, and toko fire. When 

 subjected to distillation they afford a changed fluid oil, carburotted hydrogen, and the 

 other products of oily bodies. Exposed for a certain time to the atmosphere they 

 become rancid, and generate the same fat acid as they do by saponification. In their 

 fresh state they are all composed principally of stearine, margarine, and oleino, with a 

 little colouring and odorous matter ; and in some species, hircine, from the goat ; 

 phoconine, from the dolphin ; and butyrine from butter. By subjecting them to a 

 great degree of cold, and compressing them between the folds of blotting-paper, a resi- 

 duum is obtained, consisting chiefly of stearino and margarine ; the latter of which 

 may be dissolved out by oil of turpentine. 



Beef and Mutton Suet. When fresh, this is an insipid, nearly inodorous fat, of a 

 firm consistence, almost insoluble in alcohol, entirely so, if taken from the kidneys 

 and mesenteric web of the ox, the sheep, the goat, and the stag. It varies in whiteness, 

 consistence, and combustibility, with the species and health of the animals. They 

 may all be purified in the manner above described. Strong sulphuric acid developes 

 readily the acid fats by stirring it through melted suet. Alkalis, by saponification, 

 give rise to one of the three acids, the stearic, margaric, or oloic. Beef suet consists 

 of stearine, margarine, and oleine ; mutton and goat suet contain a little hircine. The 

 specific gravity of the tallow of which common candles are made is, by lire's experi- 

 ments, 0'936. The melting point of suet is from 98 to 104 F. The proportion 

 of solid and fluid fat in ib is somewhat variable, but the former is in much larger 

 proportion. Mutton suet is soluble in 44 parts of boiling alcohol, of 0*820 ; beef 

 suet in 44 parts. Marrow fat consists of 76 of stearine, and 24 of oleine ; it melts at 

 115F. 



Hog's lard is soft, fusible at 81 F, convertible, by an alkaline solution, into a 

 stearate, margarate, oleate, and glycerine. Its sp. grav. is 0'938, at 50 F. It con- 

 sists of 62 of oleine, and 38 of stearine, in 100 parts. 



Goose-fat consists of 68 oleine and 32 stearine. 



Butter, in summer, consists of 60 of oleine and 40 of stearine ; in winter, of 35 of 

 oleine and 65 of stearine; the former substance being yellow and the other white. It 

 differs, however, as produced from the milk of different cows, and also according to 

 their pasture. 



Chevreul investigated with great care the composition of fats. Ho lias shown 

 that they are mixtures of simple fats as oleine, stearine, and margarine. For his in- 

 vestigations, see those articles in Watts's ' Dictionary of Chemistry.' 



The following statement is given on the authority of Braconnot : 



Hog's lard . 

 Ox marrow . 

 Goose-fat 



Oleine Stearine 

 62 38 

 24 76 

 68 32 



Duck-fat 

 Ox tallow . 

 Mutton suet. 



Oleine Stearine 

 72 28 



25 75 



26 74 



The late Dr. Kobert Dundas Thomson gave the following list of animal fats and 

 their melting points : 



Badger-fat 

 Beef tallow 

 Calf 

 Camel 



Cochineal fat 

 Cow's butter 

 Duck-fat . 

 Dog . 

 Fox . 

 Hare . 

 Hog's lard . 

 Horse grease 

 Human fat 



109 

 113 

 120 

 109 

 111 

 109 

 109 

 120 

 278 

 93} 

 105 

 115 



The purification and decoloration of fats have been the object of many patents. 

 One of the best is to mix 2 per cent, of strong sulphuric acid with a quantity of 

 water, in which the billow is heated for some time with much stirring ; to allow tho 

 materials to cool, to take off tho supernatant fat, and to ro-mclt it with abundance of 



